Help me get imaging...please!

[Muddy Diver]

Wasn't sure which thread to post this in but feel I may get some help in this one.

It is clear that I am never going to achieve half decent planetary images using just a telescope and a camera having been reading more threads covering this topic. I have a 102mm dia mak which does not lend itself greatly towards imaging, or so i understand due to the ratio of FL to aperture giving me an F13 (I believe that the lower the f number the better).

Question is, do i go for a barlow to increase the size of the image or a televue which, i may have mistakenly understood, does something subtly different. From what I understand a barlow would be ok for viewing but the televue powermate is better for imaging and this appears to be due to the higher magnifications.

Q1 How does this affect the telescopes calculated limitation of magnification?

The way I'm thinking here is if a barlow lens (2X) used with a 25mm ep gives an effective 12-13mm magnification, then using a 5X powermate as i know Iceman does will take my scope way outside of its limit,

Q2 Is there another rule for imaging?

Q3 If the members had the choice given my telescope, what decision would you make, Barlow or powermate and what size?

[ving (David)]

televue is a manufacturer of a barlow called powermate i believe. I dont know much about imaging so i cant help you there really.
someone will come along and 'elp real soon

[Striker (Tony)]

The F ratio wont stop you...the lower F ratio just means quicker imaging meaning less time exposure is needed....I cant see why you cant image with your Mak...Whats the focal length of the Mak....and what type and way do you want to image.

I am imaging at F10 at the moment with a Focal length of 2800mm

Putting a 2x barlow doubles your scope to F26

[Muddy Diver]

Whats the focal length of the Mak....and what type and way do you want to image.

Thanks Striker

So, the F ratio wont stop the little nexstar eh? Just needs longer exposures.. makes perfect sense.

Focal length is 1325mm. I havent chosen a fully developed method of imaging as yet. I plan to use either toucam or neximage, prime focus for planetary imaging mainly plus maybe some more visible nebulae. Thing is I eventually need a barlow or powermate. As ving mentioned, they could be the same item just branded differently.

[rumples riot]

Muddy,

With imaging the planets the higher the f number the better. In your case the f13 is fine. The diameter of the scope will prevent large image scales being obtained, but you should get a good start. Like suggested I would get a 2x barlow. Don't bother with a powermate yet as a 2.5 will push you over the photographic limit of the scope. A scope can go much higher in magnification under the photographic limit than visually.

If you have a 102mm scope with f13 with a 2x barlow your magnification will be 442x. If you consider that you will get visually around 40x per inch of scope and the 102 is 4 inches then 160x is max for visual and 442 will be near max for photographic.

I would not buy a 5x powermate for that scope. It will produce bad results. It will be too powerful. So I think you should get a TV 2x barlow (they are good quality) and use the neximage directly into the barlow, you should get some useful imaging practice. Or you could get a 1.5x barlow (TV does not make these) and this would lessen your magnification and produce slightly better results given the diameter of the scope.

In terms of rules for photographic magnification I have found that with my scopes of around FL2350-2500mm f10 with a 2.5x powermate a mag around 1000x is the upper most limit in average seeing. Anymore than that the image breaks down very quickly. That means effectively a 10" will support something around 100x mag per inch for photographic use in average seeing. In excellent seeing this may go as high as 125x. Only seen this once in the last year. For a 9.25 the effective photo mag is just a bit over 100 times in average seeing.

So to sum up, get a 2x barlow and try for saturn or Jupiter or the moon and see how this goes. If your unsure get a slightly smaller barlow first and see if you can borrow a 2x from someone else.

Best of luck.

Paul

[Robert_T]

Hi Muddy - second what Paul/Rumples says below. This setup should be fine for lunar and planetary imaging with toucam or neximage (I'd recommend the latter as it's all setup to go for astro and has the same innards as Toucam - it's what I use so I'm biased). Both can have a long exposure modification done, but your setup at F13 and small aperture really would not be very suitable for any deep sky work except maybe brighter star clusters. Still you can hone your skills and maybe get more suitable gear for this down the track if that's the way you want to go.

cheers,

[Muddy Diver]

Paul/ Robert


Good advice which will save me much frustration i think. Appreciate the help, I can now plan my next shopping spree. (it seems continuous at present).

Cheers

[Dennis]

Hi Muddy

I second all the sage advice from the IIS gurus, above. I started with a Vixen 102mm f9 'scope and there is a lot to achieve and learn, even with such a relatively modest aperture.

At a focal length of 918mm for the Vixen, the TeleVue x2.5 gave me a nice image scale and was reasonably immune to all but the worst seeing. I suspect your main challenges will be:

Acquiring the planet in the field of view.
Keeping it there.
Focusing.

Once you have mastered these, it becomes an enjoyable if slightly obsessive past time. The gang at IIS has been an inspiration to me and hanging out here has also taught me a lot. Don't be put off by early difficulties as you struggle to master your equipment - practice will pay off in the end.

Good luck!

Dennis